Currently, subsea fields located where sea bottom temperatures and flowline pressure are in the wax region and/or in the hydrate region are developed with a heat retention (HR), or heat retention and heat addition (HRAHA) strategy for the flowline back to topsides. These HR and HRAHA systems may have one well or multiple wells. The multiple wells, HR and HRAHA systems may have numerous configurations: (i) multiple wells feeding one manifold that is connected by a flowline system back topsides, (ii) multiple multiple-wells manifolds feeding a flowline system back topsides, (iii) multiple wells feeding a flowline system back topsides, and (iv) one or more wells, and one or more manifolds feeding a flowline system back topsides.
Recently, it has been proposed that these fields could be developed with a cold flow strategy. In contrast to the currently used strategies, a cold flow strategy allows or promotes precipitation and produces a transportable slurry stream, which moves to a distant topsides flowline that does not have to retain or add heat.
Two well-stream-collection strategies have been proposed for cold flow systems:
In the SINTEF system, the cold flow system is started with one well stream and a re-cycle system. Then, additional single unprocessed well-flow-streams are added to the processed stream (one by one).
In the other systems, a stream from one or more nearby wells is used as the single input to the cold flow processing system, and then the processed stream is sent to the topsides facility.
U.S. Patent Application Publication Number 2006/0175063 discloses a system for assuring subsea hydrocarbon production flow in pipelines by chilling the hydrocarbon production flow in a heat exchanger and causing solids to form, periodically removing deposits and placing them in a slurry utilizing a closed loop pig launching and receiving systems. U.S. Patent Application Publication Number 2006/0175063 is herein incorporated by reference in its entirety.
There is a need in the art for improved cold flow systems which can operate without adding heat.